Hybrid and electric vehicles depend on a traction battery to supply energy for propulsion and accessory loads. The traction battery may be made from a variety of chemical formulations. A traction battery may be made from a lithium-ion compound. A characteristic of a lithium-ion battery is that the capacity of the battery tends to decrease as the battery ages. Over time, the battery may be subjected to repeated charge and discharge cycles. As battery charge capacity decreases, less energy is stored in the battery which may lead to a decrease in vehicle performance. For example, an electric vehicle may experience less range on a full charge. A hybrid vehicle may experience a decrease in fuel economy as the gasoline engine may need to be operating longer.